4994-87-0Relevant academic research and scientific papers
2-acylamino- and 2,4-bis(acylamino)pyrimidines as supramolecular synthons analyzed by multiple noncovalent interactions. DFT, X-ray diffraction, and NMR spectral studies
O?mia?owski, Borys,Kolehmainen, Erkki,Ikonen, Satu,Valkonen, Arto,Kwiatkowski, Adam,Grela, Izabela,Haapaniemi, Esa
, p. 9609 - 9619 (2012)
Intermolecular interactions of ten 2-acylamino and 2,4-bis(acylamino) pyrimidines (7 of which are previously unknown) have been investigated by X-ray structural, quantum chemical (DFT), and NMR spectral methods. Especially the concentration dependencies of the 1H NMR chemical shifts and titrations with other molecules capable of multiple hydrogen bonding provided useful information regarding their association via triple or quadruple hydrogen bonding, which is controlled by the conformational preferences of 2-acylamino- and 2,4-bis(acylamino)pyrimidines. On comparison of the properties of 2-acylamino- and 2,4-bis(acylamino)pyrimidines with the corresponding pyridines, an additional nitrogen in the heterocyclic ring is the crucial factor in explaining the stability of various conformers and dimers of pyrimidines. Computational modeling of their dimerization (self-association) and heteroassociation supports the experimental findings. The substituent effects in 2-acylamino- and 2,4-bis(acylamino)pyrimidines are discussed via inter- and intramolecular terms. The subtle balance between several structural factors and their influence on the aggregation of studied pyrimidines was confirmed also by variable-temperature NMR and NOE experiments. X-ray structures of 2-methyl- and 2-adamantyl-CONH-pyrimidines revealed very different intermolecular interactions, showing the importance of the substituent size on the self-assembly process. As a whole NMR spectral, X-ray structural, and computational data of 2-acylamino- and 2,4-bis(acylamino)pyrimidines can be interpreted in terms of multiple intra-/intermolecular interactions.
Prolinamides of Aminouracils, Organocatalyst Modifiable by Complementary Modules
Ruíz-Pérez, Karen M.,Quiroz-García, Beatriz,Hernández-Rodríguez, Marcos
supporting information, p. 5763 - 5772 (2018/11/10)
We report the synthesis and evaluation of prolinamide organocatalysts that incorporate aminouracils. The features of these catalysts are enhanced NH acidity of the amide because of the electron-withdrawing nature of the heterocycle, an additional hydrogen-bond donor at the α or β positions of this functional group (using 6-aminouracil or 5,6-diaminouracil respectively), and it can be recovered due to its low solubility and used again without decreasing the enantioselectivity. A unique feature of these systems is the self-assembly capability with complementary modules by Watson–Crick interactions. These supramolecular adducts behave differently from the catalyst alone, some of them have lower performance but others improve the selectivity of the product. Therefore, this approach avoids the synthesis of many catalysts.
